1. Field of the Invention
The present invention relates, generally, to tracking apparatus and methods and to augmented reality (AR) technology for integrating or augmenting real information such as actual or captured real-world images with virtual information such as images of computer-generated objects. More particularly, the invention relates to a fiducial-based tracker or to a fiducial-based means for registering the virtual-world information to the real-world information within an AR system.
2. Background Information
AR technology allows a person to see or otherwise sense a computer-generated virtual world integrated with the real world. The xe2x80x9creal worldxe2x80x9d is the environment that an observer can see, feel, hear, taste, or smell using the observer""s own senses. The xe2x80x9cvirtual worldxe2x80x9d is defined as a generated environment stored in a storage medium or calculated using a processor. A tracker system within the AR technology registers the virtual world to the real world to integrate virtual and real information in a manner usable by the observer.
AR technology essentially xe2x80x9cconnectsxe2x80x9d a human user to a database or to a virtual or partially virtual environment using any combination of the human user""s visual or aural or kinesthetic senses. Alternatively, AR technology can be viewed as connecting the partially virtual environment to the real environment as observed by the human user. AR technology allows the human user to perceive and be guided by processed database information that is integrated with the real world. Additionally, AR technology may enable a human to participate in an activity in a virtual world by translating the human user""s movements or activity within a defined area or volume of the real world into the desired response in the virtual world.
Visual AR technology includes xe2x80x9cVideo See Throughxe2x80x9d AR technology and xe2x80x9cOptical See Throughxe2x80x9d AR technology. Video See Through AR technology uses a camera to capture real world images and electronically adds or integrates the virtual images to create the augmented image. Optical See Through AR technology projects the virtual images on a see-through display, enabling a human user to see the projected image of the virtual object on the display and the images of the real world objects through the display.
By allowing a human to quickly, accurately and appropriately retrieve and apply virtual information to a problem, a task or situation in the real world, AR technology provides significant benefits in a society that is being inundated with information. For example, because of the quick development of many new technologies, the time required to train a person or to assemble and service complex products is increasing. New products are being quickly introduced into the market while many older generations of products are being concurrently used by the general public. An AR system can augment or enhance the real world view of the equipment with instructional text, drawings and diagrams to enable service professionals to quickly, accurately, and competently work on the equipment. There are many other examples of the benefits provided by the AR technology, including but not limited to the following examples. The invention can be used to improve the efficiency and quality of assembling or inspecting components such as televisions, radios, computers, and other components. Similarly, the invention can be used to improve the efficiency and quality of servicing or maintaining systems by superimposing text, pictures, drawings, schematics, and other information from maintenance manuals, for example, upon a real-world object. An AR system can be used to simulate real world activities, such as piloting aircraft or ships, and further can be used for instructional training, education, or rehearsals. Additionally, the invention can be used to create games or other entertainment, or to form an artistic medium by capturing and manipulating the artist""s motions. Furthermore, the invention can be used to document head and eye responses to stimuli by tracking and recording the motion of either the user""s head or the user""s pupil after a stimuli has been introduced.
The AR system of the present invention has been used to fabricate wire harnesses for commercial airline planes. Each commercial airliner typically contains hundreds of wire bundles and hundreds of miles of wire. As shown in FIG. 3, the known art requires an assembly worker to bundle the wires around pegs formed on plywood boards by viewing printouts of wiring diagrams and transposing the information to the board. The known method for fabricating wire harnesses is a slow and tedious process that can result in expensive and time-consuming mistakes, and contributes to the billions of dollars that the airline industry loses because of production delays. The boards are specially designed for various wire harnesses, and must be stored. However, the wire harness fabrication AR system embodiment of the present invention has been shown to reduce cycle time by fabricating quality wire harnesses up to 50% faster than the current methods, and enables planes, particularly the wire harnesses, to be quickly designed and produced according to the special requirements of a customer.
An AR system should allow a human user to easily and naturally interact with objects in both the real and virtual world. Therefore, a visual AR system should: (1) quickly and accurately detect and track input data such as coordinate marks or fiducials; (2) quickly process the input data to determine the relative position and orientation between the user and the target objects and register the virtual world objects to the real world objects; and (3) quickly and smoothly integrate the virtual world objects with the real world objects either by displaying or projecting an image of the virtual world objects over the real world objects or by electronically combining an image of the virtual world objects with a captured imaged of the real world objects. Therefore, an AR system should have a small latency period and a quick update rate. xe2x80x9cLatencyxe2x80x9d is defined as the period of time between the moment when the input data is captured and the moment that the augmented information is displayed or otherwise presented in usable form to the user. xe2x80x9cUpdate ratexe2x80x9d is defined as the frequency of refreshing the displayed or otherwise presented information that is processed from new input data. Humans perceive their environment with an essentially continuous update rate and zero latency period. Therefore, a human will be able to easily and naturally interact with an AR system that has an update rate and latency period approaching a human""s natural capabilities; i.e. xe2x80x9creal timexe2x80x9d or xe2x80x9cnear real time.xe2x80x9d An update rate of at least 60 Hertz and a latency period of 16 milliseconds or less is considered xe2x80x9cnear real time.xe2x80x9d
Known trackers include magnetic-based, moving infrared beam optical-based, light source (LED) optical-based, ultrasonic-based, and mechanical-based trackers. Problems associated with these trackers generally include stray fields, noise, cost, insufficient accuracy, and limited mobility. Magnetic or moving infrared beam optical based trackers have been used in fighter aircraft and helicopters. These trackers accurately measure the user""s pose with update rates of twenty Hertz or greater, but are complex systems that work within a very limited volume and severely limit the mobility of a user. Furthermore, magnetic-based trackers are sensitive to and their accuracy may be detrimentally affected by metallic objects in the vicinity of the sensors. Light source-based trackers use a camera to track various light source patterns, such as Light Emitting Diode (LED) arrays, that are placed on a surface of a target object. These light sourcebased trackers are effective in limited volumes and severely restrict the movement of the user. Additionally, these trackers have a limited accuracy and a latency greater than 100 milliseconds. Ultrasonic-based trackers are subject to noise interference in practical environments. The light source-based and ultrasonic-based trackers use xe2x80x9cbeaconsxe2x80x9d or xe2x80x9cactivexe2x80x9d fiducials. An active fiducial generates a signal that is detectable by a sensor. Mechanical tracking systems, comprising a pantograph arm attached to a head mounted display, have been used in U.S. Army gunship helicopters. These mechanical-based trackers also severely restrict the mobility of the user.
Applicants"" invention provides an AR system, including a fiducial-based tracker system, which is believed to constitute an improvement over existing technology.
The present invention provides an apparatus and method for tracking the position and orientation between at least one sensor and at least one object, wherein either, or both, the sensor and the object may be mobile. The tracker system of the present invention is used as a means for registering virtual information to real world information within an augmented reality (AR) system. Proper registration in an AR system enables a user to correctly view a virtual scene and be guided to properly place or otherwise interact with real objects in an augmented view. The registration process conducted by the tracker system calculates six tracking parameters that determines the relative position and orientation between at least one real world object or target and at least one sensor. The tracking parameters include three orientation parameters (the angles phi, theta and psi) and three position parameters (distance [L] and the intercept of the user""s line of sight with the fiducial plane [X-bar and Y-bar]). The tracker system continuously calculates or tracks these parameters because the target(s) and/or the sensor(s) are mobile.
An AR system operates within a volume formed by boundaries defined by the position of the sensor(s) and the tracked, real world object(s). The tracking system may be designed as either a 2-dimensional or 3-dimensional tracker. Additionally, the tracking system may use monocular or binocular optics to display data. The 2-dimensional tracker tracks the position of objects on an object plane, such as a wiring board. The 3-dimensional tracker tracks the position of objects on or in an object volume. The monocular AR system projects an image into one eye. The binocular tracker projects slightly modified augmented images to both eyes to enhance the augmented view with depth perception. A monocular AR system incorporating the 2-dimensional tracker may be used to fabricate a wire harness for a vehicle, aircraft, or other object. Fiducials are placed on or near the board on which the wire harness is assembled. The augmented reality technology allows a human to simultaneously view a virtual image identifying the correct wire path. Additionally, a monocular AR system incorporating the 2-dimensional tracker may be used to enhance the reading and interpretation of maps and charts. Virtual legends and text may be superimposed on a map or a virtual map may be superimposed over the real world objects. For example, a field soldier may view virtual images or information about troop movements generated by current military intelligence while viewing a real world map, and then switch perspective and begin looking around at the real world field with a virtual map properly oriented and superimposed over his current field of vision. Other examples of enhanced processes include inspection of parts and electrical panel wiring. A monocular AR system incorporating the 3-dimensional tracker may be used to wire fuselages. A binocular AR system incorporating either a 2-dimensional or 3-dimensional tracker may be used to enhance medical processes and devices, such as endoscopes and surgical devices.
The tracker system generally comprises a sensor or sensors for detecting a pattern of fiducials disposed on an object surface and a processor connected to the sensor. The sensor has a position and an orientation with respect to the pattern of fiducials on the object surface, which is identified by the processor by acquiring or matching a detected pattern of fiducials with a reference pattern of fiducials. The reference pattern of fiducials may be stored in a computer memory as a data file. In a preferred embodiment, the pattern of fiducials includes a geometrically consistent hard fiducial pattern and a pseudo random soft fiducial pattern. The hard fiducial pattern is used to identify the phi, theta, and psi orientation parameters and the L position parameter. The soft fiducial pattern is used to identify the X-bar and Y-bar position parameters.
The AR system generally comprises a pattern of fiducials disposed on an object surface, a computer having a processor and a memory, an interface for receiving input and presenting AR output to a user, and a tracker system for detecting the pattern of fiducials and determining the relative position between the user and the target object. The tracker includes at least one sensor for detecting the pattern of fiducials. The sensor is electrically connected to the computer, and has a position and an orientation with respect to the pattern of fiducials on the object surface. The processor identifies the position and the orientation of the sensor with respect to said object surface by matching a detected pattern of fiducials with a reference pattern of fiducials stored in the memory of the computer. In a preferred embodiment, the pattern of fiducials includes a geometrically consistent hard fiducial pattern and a pseudo random soft fiducial pattern, the computer is a wearable computer, the interface has an update rate of at least 60 Hertz and a latency below 16 milliseconds, and the sensor is an optical sensor or camera capable of detecting passive fiducials.
The method for tracking the position and orientation of an object generally comprises the steps of scanning across an object to detect fiducials and form video xe2x80x9cruns,xe2x80x9d clumping video runs to detect a pattern of fiducials, acquiring estimated values for a set of tracking parameters by comparing a detected pattern of fiducials to a reference pattern of fiducials, and iterating the estimated values for the set of tracking parameters until the detected pattern of fiducials match the reference pattern of fiducials to within a desired convergence. In a preferred embodiment, the step of clumping video runs includes the steps of combining adjacent video runs and only recording pixels having a video level above a predetermined threshold. The step of acquiring estimated values for a set of tracking parameters includes the steps of corresponding a predetermined number of detected hard fiducials with a reference pattern of fiducials to estimate the orientation parameters and the distance position parameter, and electing at least one of the soft fiducials with the reference pattern of fiducials to estimate the X-bar and Y-bar position parameters.
The method for augmenting reality generally comprises the steps of disposing a pattern of fiducials on an object surface, tracking the position and orientation of the object, retrieving and processing virtual information stored in a computer memory according to the position and orientation of the object, and presenting the virtual information and the real information to a user in near real time. In a preferred embodiment, the pattern of fiducials include a geometrically consistent hard fiducial pattern and a pseudo random soft fiducial pattern; and the steps of tracking the position and orientation of the objection, retrieving virtual information, and presenting the virtual information with real information are performed with an update rate of at least 60 Hertz and a latency below 16 milliseconds.